Automatic telephone system.



B; n. Wnms.v AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JUNE 7. 1916. 1,315,442.

Patented Sept W/T/VEJSEJ B. 0., WILLIS. AUTOMATIC TELEPHONE SYSTEM.

1,315,442 APPLICATION HLED JUNE 7, 1916. Patented-Sept. 9,

j (xi/v va.

W/T/VEJSES B. WILLIS. AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED JUNE 7. 1916.

Patented Sept. 9, 1919.

4 SHEET$SHEET 4 ham 5555 UNITED STATES, PATENT orrron.

BERNARD D.' WILLIS, OF CHICAGO, ILLINOIS, ASSIGNORTO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATIONLOF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM. I

To all whom it may concern:

Be it known that I, BERNARD D. WILLIS, a citizen of the United States of America, and a residefit of Chicago, county of Cook, and State of Illinois,have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My. invention relates in general to automatic telephone systems and is particularly concerned with the handling of long distance connections in such systems. More specifically, my invention discloses improved means for completing long distance connections to local subscribers served by a mode-rn automatic central exchange.

The principal object of my invention is the provision, in a system of automatic toll service trunks entirely separate from the regular trunking system, of 1mproved-con-- trolling circuits for the automatic switches and improved supervisory circuits for the toll operator, tails of circuit arrangement, whereby toll connections involving a minimum of transmission loss may be completed automatically .with rapidity and certainty.

Theforegoing and other objects of my invention and the preferred means for carrying out the same, will appear moreclearly and will be explained more fully herein.- after, reference being had to the accompanying drawings, in which Figures 1, 2, 3, and 4, when taken in order with the lines at the ends thereof in alinement, represent diagrammatically a complete long distance connection between a calling substation A,'in a manual exchange, and acalled substation A, in an automatic exchange. The said connection has been established through the medium of the operators cord circuit 0 (Fig. 1), the toll line,3031,connecting the two exchanges, the operators cord circuit 0 (Fig. 2)., the toll service trunk 103-104, the

toll selector E (Fig. 3), the toll selector E,

.and as shown herein consists ofthe usual common battery arrangement in which the Specification of Letters Patent.

together with certain other de- Patented Sept. 9, 1919.

' Application filed June 7, 1916. serial No. 102,180.

transmitter and receiver are connected in ser1es.- The l1ne conductors 11 and '12 have allotted to them at the exchange the usual line and cut-ofi' relays 14 and 15, the answermg ack J, and the lamp signal L.

' 'The toll operators cord. circuit 0 may likewise be of any suitable type. As shown here n it comprises. essentially a bridged relay 17 which, in conjunction with sleeve relay 16, controls. the supervisory lamp L, and the ringing up looking relay 18 which, 1n cQn unction with sleeve relay 19, controls the supervisory'lamp L Keys K and K are ringing keys, while key K is a listening key whose function it is to bridge the operators head set across the two strands of the cord circuit.

The toll operator having the cord circuit-- 0 has access to a number of toll line extendlng to the dlstant automatic exchange and terminating there at a toll board hefore other operators. One of these tolllines is indicated by reference characters 30 and 31 and extends from ack J at the toll board in the manual exchange to the ack J at the toll board in the automatic exchange- In addition to the jacks J and J which may be multiplied if desired, the toll line 30- 31 is provided at each end with a regulation It is to be understood that the equipment described thus far, including all that shown in Fig. 1 and the line equipment belonging 'to the toll line 3031 and partly shown in Fig. 2, is-old and well known, and has been included simply to facilitate an understanding of theinvention.

The cord circuit 0 (Fig. 2), while it resembles other well known cord circuits in a great many respects, is nevertheless considerably modified in order to reduce transmission losses and to enable it to cooperate with the special toll service trunks, a single. supervisory bridge comprising the lower ginal-sleeve relay-43, while the lamp L is construction toselector E. The toll selector a special supervisory signal .controlled by E is operable in responseto the second digit the same relay and Whose function'it-is to inform the operator when abusy line has 3 become id1e,allof which-will be fully explained hereinafter. Key-K is provided to enable the operator.. to shift the control of relay 43 from one lamp to the other. Keys K and K7 are the eigulai' ringing keys.

10-The doublethrow ke tening and monitoring key. 'When thrown in one .direction the operators head set is. bridged across theatwo strands of the cord' circuit in the regular manner, .but when thrown in-th'e opposite direction t e relay 51 is operated, whereby the receiver in series with theresistance 52 is connected across the cord. circuit for monitoring purposes. The double throw key K is provided to enable the operator to'open the cord circuit conductors on either side of her 'listening' key, whereby she is able-to cut ofl? the sub scriber at either end while talking to the subscriber at the other end., The key K is a calling device key throu h the medium of whichthe operator mayhinsert the calling I device S in the sleeve conductor of the cord.

The calling device S may be commonto a 1 number ofcord circuitsand as shown herein 30. of the well known two-wire type, such as .is disclosed in the British patent to Dicker,

' 'No. 296,54. of 1910.

1 The 'tolloperator at the to ll board in the automatic exchange, whose cord. circuit .0 'has1ustbeen described, has'before her the multiplev jacks ofa" group of'toll service 'trunks eachof which extends to a toll first selector, ,One of these trunks may be seen i extending from jack J ,-(Fig.2) by wayof .40.- repeating 'coil R and cond-uctors'103'and 104' to the-toll first selector E' (Fig. 3). The ap-Q paratusjust below the repeating coil R and I indicated collectively by reference character M is individual to the toll service trunk ter- ,minating in jack J It comprises a group of relays whose functions can best explained in the detailed description of the operation. '1 d The toll selector E U. S. Letters Patent No. 815,321,.granted March 13, 1906, to Keith,-'Erickson, and Erickson; being, however, more nearly of the particular type disclosed in the British patent to the Automatic Telephone Mfg. (30., No. 2543 of 191a. Such a selector'switch,-

as is. well known, may beoperated in response to the first digit of a called number is a combined 1is-.

. known manner when the subscriber at sub- (liig. is of the env 50 eral type of selector switchdisclose in selector E, one of these trunk lines being ShOWIl extending from bank contacts 213, 214, and 215 to the toll connector F (Fig. 4) The toll connector F is of the general type of connector switch disclosed in U. S. Letters Patent No. 815,176, granted March 13, 106,110 Keith, Erickson, and Erickson; being modified, however, to a considerable extent in order to help accomplish the objects of my invention. The connector switch F is given access .to a single group of subscribers lines fand is operable in response'to the two .final digits'ofa called number to establish connectionwith any line in thegroup to which it has access.

One-of the subscribers"line s to which the toll connector has access, is shown extending from the bank contacts 324, 325 and 326 to 90. the substation A. This substation may .be of any suitable automatic type such, for ex ample, as is shown in the British patent to Martin, No. 141901": 1910. For calling pur-. poses theline conductors of substation A are provided-at the exchange with an individual line switch indicated by reference character 0. The-line switch C is of the.

general type of line switch disclosed in the- British patent to James, No.26301 of 1906; being, however, of the particular type disclosed in U. S. Letters Patent No. 1,078,690,

' granted Jan. 17, 1912, to Frank Newforth;

The line switch C is operable in a well station A: is calling to extend connection to an idle selector switch.

To sum up the foregoing briefly in order that the trunking scheme may be fully comprehended, the subscribers lines in the automatic exchange are divided in the well known manner into a large number of groups, each group being provided with a plurality of connectors which are accessible through the medium of the regular line and selector switches to calling subscribers and which have access to called lines in their associated groups. In addition, each group v ofsubscribers lines is provided with -a separate and lesser plurality of toll connectors, 12

similar to toll connector F, which are accessible only to the toll operators through the medium of selectors E and E. It will be seen, therefore, that the exchange com prise two separate and distinct trunking systems, one of which is used by local subscribers for completingconnections to other local subscribers, while the other is used by toll operators for completing long distance connections to the'same local-subscribers.

nection with the toll connectors F I have shown a ringing current generator Gen for.

signaling purposes and a busy machine Q" for supplying a busy signal to the operator when the called line is busy.

Having given a briefdescriptionof the.

apparatus, I'will now proceed to a more detailed description of the operation of the same. For the purposes of the'explanation it will be assumed that the'subscriber at substation A. (Fig. 1) desiresto obtain a "con nection with the subscriber at substation A:

(Fig. 4), this beingthe complete circuit connection shown in the drawing and previously referred to.

Referring now -to Fig. 1, the substation the answerin jack J.

A is shown as having at the toll operators position. s, of course, would be the case only in a smallexchange, but since the method of receiving toll calls in a large exchangeis somewhat complicated, involving as it' does a subscribers operator and a so-called record1ngop-' erator, the present showing is preferred on account f its slmpllcity.

Upon removing hlS receiver to initiate the call, the subscriber at substation A com- 'pletes an energizing circuit .for the linerelay 14, thereby lighting the lamp signal L to attract the attention of the operator. Up on perceiving the signal, the operator Wlll 1nsert the answering plug of an idle cordcircuit (cord circuit 0 in thls case.) in the answerin' jack J and will then throw her listening ey K? andianswer the call. Communications having been established with the operator, the; calling subscr ber gives her the usual information regarding the party wanted and also his' own name and telephone number, and then replaces his receiver.. I

Since. the required party a subscriber 1n the distant automatic exchange, the toll operator will now insert the calling plug of her" cord circuit in the multiple pack J and operate her ringing key," thereby actuating .the drop 32 at the distant exchange. In response to the signal thus displayed, the toll operator having the cord circuit 0 Wlll answer by inserting the answering plug of such cord circuit 'in jack J 2 and operating her listening key; Since the particular routine followed by the operators .in setting'up a connection, including the making'out of toll tickets, timing and supervising the connection, etc., variesgreatly'with the difi'er-' entoperating telephone companies and since this invention isnot particularly concerned with these details, the description of this part of the operation: will be very general.

tion, which in accordance with myfinvem fclosed by the insertionof the plug, sleeve of manner. 1 Relay 105,upon energizing, com- ;ture, prepares an energizing circuit for re- "lay'109 and also closes a circuit to the busy [lamp L as follows: ground at G", contact springs 121 and 120,'and lamp L 'to battery j lamps, associated-with the multiple jacks of I spring pairs 130 129 and 133- 132 in ing toll operator is given the telephone number of the required subscriber and that she immediately proceeds to'set up 'the conne'c-' 70 tion is done substantially as described here inafter.v Observing. first that the service circuit over the sleeve of the cord: ground 'at'-G contact springs 139and 138, winding 106 of relay 105, contact springs, ofjack J 3 jack-J sleeve of plug,'contact springs of key K9, and winding of sleeve relay 43 to fbattery. B Relay 43, upon ener 'zing,

lights the supervisory lamp L in an o vious I 1 letes-a circuit for slow-actingrfela 108 as ollows: ground at G, contact 'spr1ngs1-17 and 118, and winding of relay 108 to battery B Relay 108, upoIi attracting itsarmae B It" is tobe understood that other busy service trunk 103-104 in other positions, are connected in multiple with lamp L and are lighted at the same time.

, As a further result of the energization of relay 105, a circuit is closed for the linere-= lay 150 of the selector E. (Fig. 3) as follows: ground at. G, contact springs 114 and 115, contact springs 135 and 134, windings 112 and 113 of relay 111 in parallel, contact parallel, windings 102 and 101 of repeating coil R in parallel, conductors 104 and 103 in parallel.,'norma'lly closed contact spring pairs of relay .155 in parallel, and windingsw 152. and 1510f the line relay 150 in parallel to battery B Relay 111 is differentially wound and is not operated upon the closure of the above circuit. Relay 150, however, attracts its armature and thereby "closes an energizing circuit for the slow-acting relay 115 153, which relay, upon energizing, prepares circuits for the vertical and rotary magnets 157 and 158 in the well known manner.

' .The foregoing operations have ',-taken V place as a result of the insertion of the plug 12 the resistance 44 and the calling device S are substitntecl for relay 43 in the circuit of relay 10 5. The'supervisory lamp Liis, of course, temporarily extinguished. The manipulation of the dial of the calling device S in accordance with the first digit of the desired number results in a number of interruptions of the circuit of relayl05. At the first retraction of its armature, relay 105 completes a circuit for slow-acting relay 109 as .follows: ground at G, contact Springs 117 and 116, contact springs 123 and 122,

and Winding of relay. 109 to battery B Relays 108 and 109, being slow-acting, retain their armatures in operated position during the operation of relay 105 in response to the calling device S, after which relay 109 again retracts. its armature. In its operated position relay 109, through the medium of contact .springs' "124-127 inclusive, short-circuits the windings of relay 111.

It will be clear now that at each deenergiza-- tion, relay 105 interrupts the circuit of the line relay 150 of the toll selector E, the successive closures of the circuit between interruptions being by way of a direct path via conductor141-and the contact springs of relay 109.

. As a result of these interruptions of its circuit the line relay 150 denergizes a corresponding number of times, and sends at each deenergization an impulse from ground .at G tothe slow-acting relay 154 and the vertical magnet 157 in series.

The vertical magnet in response'to these impulses steps up the switch shaft until the wipers 170, 171,

and 172' stand opposite the horizontal level v in which are located contacts lyhichare terminals of the desired group of'trunk lines.

The relay 154, being slow-acting, retains itsarmature during the series of impulses and closes a circuit for the test relay 156, which latter relay prepares a circuit for the rotary magnet 158 and locks itself to ground at G. Atthe end of the series of impulses v the relay 154 deenergizes, thereby completmg the aforementioned circuit of the rotary denergizes and o ens the rotary magnet circuit, thereby bringing the wipers to rest upon the terminals of an idle trunk line, as-

sumed to be in this case the contacts 173, 174, and 175. As a further result of the deenergization of the test relay 156, a circuit is completed for the line switching relay 155' which relay, upon energizing, disconnects the conductors 1.03 and 104 from the windings of the line relay 150 and extends them by; way of wipers 17 0 and 172', bank contacts 173 and 175, and normally closed contacts of relay 203 to the double wound line relay 200 of the toll second selector E.

As is well kndwn,.:the rotary- The line relay 200 thereupon energizes over the previously traced circuit extending from ound G over the two conductors 103 and 104 in parallel and completes an. energizing circuit ,forthe slow-acting relay 201. Relay 201, upon attracting its armature completes a holding circuit for the switching relay, 155 of selector E over the following path: ground at G, contact springs 204,

bank contact 174, wiper 171, normally closed contacts of relay 156, and winding of relay 155 to battery B Itwillbe-understood that the slow-acting relay 153 retains its armature for a sufficient length of time following the deenergization of line relay 150 to prevent the release of the selector until the above holding circuit has been established.

The toll operator may now manipulate her calling device in accordance with the second-digit of "the desired number, whereupon the resulting interruptions are repeated as before by the relay .105 until they. affect the line relay 200 of the toll second selector E. The selector E is accordingly operated substantially as described in the case of selector E to raise the wipers 210, 211, and 212 until they stand opposite the horizontal level which contains terminals of trunk lines extending to the desired group of connectors. After the level selection has been acomplished the wipers are automatically rotated-to select an idle trunk line, and the trunk .line selected is assumed .to have been in this case the trunk line extending to the connector F. Through the medium of the line switching relay 203 the extended conductors 103 and 104 are then disco'nnected from the line relay 200 and are further extended, respectively, by way of wipers 210 and 212, bank contacts 213 and 215, and contact spring pairs 274273 and 27 027 1 of relay 252 to the line relays 250 and 251 of the connector-F. It should be noted that the lower conductor 104 also passes through contact springs 295 and .293 of busy test relay 262 before reaching the winding of line relay 251. The line relays 250 and 251 are accordingly energizedover a previously traced circuit extending from ground at Gr via conductors 103 and 104 and attracts their armatures, relay 250 closing thereby a circuit for the slow-acting relay 258. as follows ground at G, contact springs 283 and 284, and winding of relay 258 to battery B Upon energizing, relay 258 completes a holding circuit for the switching relays: in the'selector switches as follows: ground at G, contact springs 288 and 289, bank contact 214, and wiper 211 to wire junction .217, where the circuit'divides, one branch extending by way of normally closed contacts of relay 206 and the winding of switching relay 203 to battery B and the other branch extendingby way of 0&-

the vertical magnet 304- over the following path: ground at G, contact springs 281 and 280, contact springs 286 and 287, winding of relay 260, contact springs 297 and 296, contact springs 291 and 294, winding of vertical magnet 304, and side switch wiper 302 (in first position) to battery B. In response to these impulses the vertical magnet steps up the switch shaft until the wipers 321, 322 and 323 stand opposite the horizontal leve of bank contacts in which are located contacts of the line. extending to substation A. The private control relay 260 is energized in series with thevertical magnet and, bein slow-acting, retains. its armature attracte during the series of impulses to close a circuit in the regular manner for the private magnet 263. At the end of the series of impulses relay 260 and the private magnet denergize', the latter controlling the side switch wipers 301 and 302 in the well known manner to advance them to their second position.

The toll operator may now operate her calling device in accordance with the final digit of the desired number, resulting as before in denergizations of line relays 250 and 251. As before, .the line relay 250, at

each denergization, transmits an operating impulse over a path previously traced, except that now, side switch wiper 302 belng in its second position, these impulses pass through the rotary magnet 305. In responsethereto, the rotary magnet operates to rotate the wipers 321, 322, .and 323 until they arrive, respectively, at bank contacts 324, 325, and 326,. which-contacts are associated with the line extending to substatlon A. As before, the private magnet 263 is maintained energized during the series'of. impulsesthrough the medium. of relay 260 and operates at the end of the series-of 1mpulses to advance the side switch wipers to their third position (it being assumed that the line of substation A was idle when called). It is to be noted here that the PI].- I

vatemagnet 263 holds the circuit of relay 265 open during the rotation of the. wipers so that if the private wiper 322 should pass over busy or grounded contacts before arriving at contact 325 the relay 265 will.

not be energized.

As side switch wiper 301 comes lnto its third position the following circuit is c0m-' pleted: ground at G 3, side switch wiper 301,

'private'wiper 322, bank contact 325 and holding winding 330 of line switch C to battery B Thecut-off armature 331 is thereupon attracted to disconnect the line of sub- 1 station A from its connections in ,line switch 0. A branch of the above circuit extends. from contact 325 to multiple con-. tacts in the banks of the remaining connectors, both toll and local, whereby the line of substation A is made busy to other calls.- A second branch extends from side switch wiper 301 by way of contact springs 306 and 307 of the private magnet and winding of relay 265 to battery B Relay 265 is operated over the foregoing branch circuit and connects the line wipers 321 and 323, respectively, with the upper and lower talking conductors of the connector.

Having finished dialing the number, the toll operator will now restore the calling device key K". Y The relay 43 is thereby again included in the sleeve circuit and operates -to light the lamp signal L as before. The called subscriber is signaled by the operation of the ringing key K of the cord circuit. When key K" is operated, a grounded ringing current generator (not shown) is connected with the tip strand of the calling end of the cord .and direct ground is connectedwith the ring strand. This is obviously a common method ofprojecting ringin current over a called line to operate a bridged signal and the ringing key K is so arranged to adapt it for signaling over toll lines, etc., as well as over the service trunk 100 shown. To proceed with the ringing opera- 5: tion, when key K is operated the following circuit isclosed: ound at G lower contact of key K, ring of plug, ring. spring Y of jack J winding of relay tact springs 136 and 137 to battery B Upon energizing, relay 110, through'the medium of contact springs 128, 129, and 130, disconnects conductor 143 from winding 112 of relay 111 and connects it instead to con- .110 ductor 104, thereby short-circuiting winding 102 of repeating coil R; and, by means of contact springs 131, 132, and 133, disconnects conductor 142 from winding 113- of relay 111 and connects it instead to 115 ground. As a result of the .foregoingcircuit changes the effect of the ringing current from key K is localized (winding 102 of repeating coil B being short-circuited); relay 251 of the toll connector retracts its armature (conductor 143 having been disconnected from ground at G) and relay 250 is maintained energized over the following path: ground at G, contact springs 131 and 132, conductor 142, winding 101 of re-. 12b peatifng coil R to conductor 103 and thence over the previously traced circuit to battery B by way of winding of relay 250. An energizing circuit has now been completed for the ringing relay 264 of the connector 110, and con- 105 the bell ata called as follows: .ground at G contact springs 281 and 282, contact springs 278 and 279,- winding of relay 264 and side switch wiper 302 to battery B he ringing relay 264,

upon energizing, operates to bridge the ringbell, the following circuit is closed: ground at G", winding 257 of retardation coil 253, windin 255 of relay 252, contact springs 308 an 309, contact springs 312 and 313, wiper 323, bank contact 326, to and through substation A, bank contact 324, wiper 321, contact springs 314 and 315. contact springs 310 and 311, winding 254 of relay 252, and winding 256 of retardation coil 253 to battery B 'Upon the closure of the foregoing circuit, relay 252 attracts its armature with the following results: ground at Gr is extended via contact springs 277 and 27 6 to the slow-acting relay 258, whereby this relay may be maintained energized independent of relay 250; and,zthrough the mediumcf contact springs 2 0-275, inclusive, the incoming line conductors are disconnected from the line relays 250 and 251 and are connected instead with thewindings of relay 252 in parallel with the called line.

It will be remembered that the relay 111 if 2) has remained inoperative up to this time owing to its differential winding. Now when the extended conductor 104is disconnected from the battery 15 by way of relay 251 and is connected'instead to ground G as described, relay 111 is unbalanced, attracts its armature, and is maintained energized over a circuit which may be tracedfrom ground G" through the right-hand windings of coil 253 and relay 252 to the lower heavy talking conductor, thence back through the wipers of selectors E and E to conductor 104, thence by way of winding 102 of repeating coil R, conductor 143, con tact springs 129 and 130, windings 112 and 113 of relay 111 in series, contact springs 133 and 132, conductor 142, and winding 10].

of repeating coil R to conductor 103, and thence over the upper heavy talking conductor through the wipers of selectors E and I E and the left-hand windings of relay 252 and c6il 253 to battery By the operation for relay 111,'ground G is'removed from the innctioniof its windings, battery B is disconnected from the ring spring of jack J an'd'ground G is disconnected from the junction of windings 103 and 10? of relay 1%.- "By the latter opory lamp L". By this The calling subscriber at substation A i may now be recalled to his telephone, the services of the operator at the originating exchange being required for this purpose,

whereupon the complete connection be tweenthe calling and called substations will have been established. The path for voice currents hasbeen drawn in heavy lines and may be readily traced without further explanatiom It is to be observed that the talking circhit at the automatic end ofthe connection includes 'a single high impedance bridge across the talking conductors at the cord circuit 0', arepeatingcoil R, and a single high impedance battery supply. bridge across the talking conductors at the connector switch, thereby. providing a. highly eficient connection. k

The. purpose of the retardation coil 253 in the connector is partly to increase the impedance of the battery supply bridge (relay 252), and partly to balance the called end of the connection. Since the bridged re-. lay 252 has an armature only on one end of its core the impedance of its windings 254 and 255 will be different and the line will," not be perfectly balanced. This trouble could, of course, be remedied by a special design of the windings .254 and 255 but a far simpler method is to use. a-retardation coil 253 in. the form of a relay, butKwith the armature on the opposite end as shown. The effects oi the-two armatures therefore balance each other.

When the conversation is over both subscribers will hang up their receivers. By

the replacing of the receiver at substation A the relay 17 is deen'ergized, thereby lighting the supervisory lamp L. In this inanner the operator at the originatingexchange is informed that the subscribers are tlizrough talking and-she will therefore remove both pin from the jacks, whereupon the subscri' er at substation. A is :free to run other call or to be called.

At the automatic exchange, when the sub scriber at substation hangs up his receiver the bridged-battery supply relay 252 deener'gizes, the windings of relay 111 being of high resistance, and again connects the incoming line conductors to the relays 250 and 251 and to the em pole of bat-- tery. As a result relay 111 is defineixed and short-circuits the winding 10? 105, whereupon the sleeve relay 43 cord circuit operates to thesame or another; operator in contact springs L will be extinguis of connector F, therefore, V I vate control'relay 260 denergizes after the v last series of impulses,

ator at the automatic exchange is informed that the conversation is over with, whereupon shemay withdraw both plugs from the By the removal of the plug from jack J the sleeve circuit'i's broken. and relay 105 is .denergized- Upon retracting its armature relay 105 disconnects ground G from the line conductors extending torelays 250 and 251 of the connector F, thereby causing these relays to deenergize. Relay 250, upon retracting its armature, relay 258 which relay, upon decnergizing, disconnects ground G from the holding circuit and also closes a circuit for the connector release magnet 259. The release magnet operates in the usual and well known manner to restore the connector switch to normal position after which its circuit 1s opened at the shaft controlled springs 334. By the removal of ground from the holding circuit the switching relays of selectors E andE are denergized, each switching relay closing the circuit of the assoclatedrelease, magnet, whereupon the selector switches are also restored to normal position At the in the same way as the connector. toll board the busy lamps similar to lamp hed .by-the denergization of relays 105and 108, whereupon the toll service trunk will be ready for useby establish ng a new connection;

I will nowdescribebriefly the operatlon when the called line is busy.- It 1s understood thatwhenever substation A is busy the test or private contact 325 and similar multiple contacts in. other connectors wlll I Y i In the-operatlon H the reslstance 0011 335, ground at G 'being be connected to ground.

' whenthe. pr1

is busy the 'By the closure of the above circuit the private magnet is maintained energized to retain the slde switch wipers in second osition and test relay 262 is energized with results which will be explained. Throughthe medium of 290, 291, and 294 the operatmagnet .is broken magnet 263 to battery 13.

ing circuit ofthe rotary andsaid magnet is connected in series with; relay 261. Relay 261 so as not to allow the o is of high resistance eration ofthe rotary magnet and is provi ed for a purpose to be mentioned later. Through the-medium of contact springs 292,- 293, and 295 the lower incoming heavy" line conductor is disconnected from line relay 251 and is connected instead to a lead from the busy sigthat the line isbusy. It

breaks the circuit of slow-acting if the called line" following circuit will bees v tablishedi ground 'on private bank contact, 45 wiper 322, side switch-wiper 4 position, winding of test relay 262, contact springs 300and. 299, and winding of private 301 in second Q to inform the operator naling machine will be observed that the busy machine lead has a branch extending by way of resistance coil 335. to ground. The proper conditions now exist for unbalancing the relay 111, as described in the ."case' when the" called subscriber answers, whereupon this relay is operated to extmguishthe-lamp L*.-

When the operator hears the-busy signal she need not withdraw her plug and release the switches, but instead she restores her listening key and operates the key K to shift "the control of sleeve relay 43 from supervisory lamp L to supervisory lam L The lamp L is preferably a red 1m? to distlnguish from the ordinary supervisory lampssuch' as L. The operator now pays no further attention to the call until she is reca'lledby the lighting of the lamp L which 1s brought about when the called linebecomes idle.

When the subscriber at substationAQ'as- ,sumed to have established connection with another subscriber, hangs'up his receiver, the automatic switches including the line swltch C are released and ground potential 1s removed from private bank contact 325, The private magnet and relay '262 accordlngly deenerg1z'e,i. the former allowing the s1 e switch wipers to pass 'to third position and closing the circuit of relay 265 to complete connection'to the called line, .and the latterrelaybreaking the circu it of relay 261 and restoring the lower heavy line'conductor to lts battery'connectlon atrelay 251. Dur 1ng the t1me the connector was .locked on busy, the line relay 250 was energized in series with the wlndings of relay 111 anddisconnected by the operation-of relay 111.

l 11'agai n connects ground at G to the junctlOIl'Of its windings whereupon the line relay 250 immediately energizes again. Were itnot for relay 261', which is slow-acting and whichholds the rotary magnet-circuit open,

the momentary decnergization of the line relay would have operated the rotary magnet to rotate the wipers to the nextjset of contacts.

As soon as the operator perceives the red lamp signal L, which, of course, is lighted by the denergization' of relay 111, she knows that the called line is n0 longer busy and that the connection thereto is completed.

She will therefore proceed to operate her Y ringing key, etc., in the manner already descrlbed with the result that the connection between the calling and called subscriberswill be completed as before.

While I have found. it convenient in ex- 45 tinuous section of a metallic talking circuit vcompleted after the lines are connected and plaining my invention to show and describe a certain specific embodiment thereof, I do to other types 'of automatic systems. I desire, therefore, to in clude'and have protected by Letters Patent all forms and modificationsof my invention which may come within the scope of the appended'claims.

What I claim as my invention is:

1. In a telephone system, a calling and a called line, means including a selector switch and a connector switch having access to the called line for 'connectin said lines,-a continuous section of meta lic talking circuit completed after the lines are connected and extending th ough movable terminals of said selector and connector to the called line, a relay in bridge of thetalking conductors of said section and controlled over'the called line for maintaining said section intact, and

a trunk release circuit separ'ate from said.

trolled by said relay.

2. In a telephone system, a calling 'and a called line,/means including a selector switch and a connectorswitch having access to the called line for connecting said lines, a con-' tinuous section of a metallic talking circuit completed thereafter and extending-through movable terminals of said selector and connector to the called line, a relay in bridge of the talking conductors at the connector for controlling the 'continuit of said section, and a second relay in sai connector cooperating with said first relay to control the release of 'saidswitches. 1

3. In a telephone system, a calling and a talking conductors for said selector concalled line, means including a selector switch and a connector switch havin access to the called line, for connecting sa1 l nes, a conextending through movable terminals", of said selector and connector to the called line, a source of talking current in a bridge of the talking conductors at the connector, a relay included in said bridge for directly controlling contacts in the talking conductors to maintain the continuity of said set':

tion, and an inductive winding connected in series with said relay to increase the.1mpedance ofthebridge. v

4: In a telephone system, a callmg and a called line, a trunk line terminating'inan line, a repeating coil in said trunk line, and continuous metallic=talking conductors extending from windings of said repeating coil to the-called line.

5. In a telephone system, a calling and a called line, a trunk line terminating in an automatic selector switch, means for connecting the calling line with said trunk line, a connector switch accessible to said selector switch, means for. operating said switches to extend the calling line via said trunk line into connection with the called line, a repeating coil in said trunk line, continuous metallic talking conductors extending from windings of sa1d repeating coil to the called line, an impedance bridge across said conductors, and a battery'in series therewith to supply talking current to the called line.

6. In a telephone system, a firstline and a second line, means including in serial relation and in the order named an operators cord circuit, a trunk line accessible thereto, and selector and connector switchesfor completing a continuous metallic talking circuit between said lines in two sections, a repeating coil in said trunk line for inductively connecting'said sections, a battery in a bridge of one section to supply talking current to said second line, and a signal controlling relay in bridge of the other section.

7. Ina telephone system, a first line, a trunk line in two sections inductivel con nected by a repeating coil, an operator s cord circuit for connecting said first line and trunk line, a second line meanslincluding selector and connector switches for connecting said trunk line with said second line, normany open contacts in said connection, and a rela and a battery in series therewith in a bri ge of the connected second line, said relay operable upon the response of the called subscriber to close said contacts.

8. In a telephone system, a first line, a

trunk line in twolsections inductively connected by a repeating coil, an operators cord clrcult for connectlng said first line and trunk line, a second line, means includ-' ing a plurality of selector and connector switches for connecting said trunk line with the closure of said contacts to control said signal.

9. In a telephone system, a trunk line terminating in an automatic switch, a bridge at each end of said trunk line, the bridge at one end comprising a controlling relay for said switch, a battery having opposite poles 'connected, respectively, to the middle points of said bridges, and means for intermittently I interrupting one of said battery connections terminating to operate said switch.

10. In a telephone system, a trunk line terminating in an automaticswitch, a bridge at each end of said trunk line, the bridge at one "end comprising a controlling relay for said switch, a battery having opposite poles connected, respectively, to the middle points of said bridges, means for intermittently interrupting one of said-battery connections to operate said switch, a second automatic switch and associated controllingrelay, and means whereby upon the operation of said first switch the controlling relay thereof is disconnected'and the controlling relay of V said second switch is substituted therefor in bridge of said trunk line.

11. In a-telephone system, a line, means ingluding a pluralit of automatic switches for extending sai' trunk line in successive stages into. connection with a called line, and operating magnets for each switch controlled exclusively over the two sides of theextended trunk line in parallel,

the operating'magnets of the first switch 7 controlled over a portion of said trunk line in parallel, and the operating magnets of the succeeding switches controlled over the same portion together witha second portion of said trunk line.-

12.'In a telephone system, a trunk line switch, a called line, means for controlling said switch over the two conductors of said trunk line in parallel to connect with the said called line, a, source of currentin the controlling circuit, means 0 erated there.

after to connect the two con uctors of said trunk line in series with said source, a signal, and'a relay operated over the said trunk line conductors in series to control said signal.

. 13. In a telephone system, a trunk line terminating in. an automatic connector terminating in an automaticconnectorswitch, a called line, means for controlling said switch overthe two conductors of said trunk line in parallel to connect with the said called line, a'source of current in the controlling circuit, means operated thereafter to connect the two conductors of said trunk line in series with said source, a signal,

and a relay for controlling said/Signal, said relay havinga winding in series with each cord circuit and trunk line, a calle in. automatic connector 1 conductor ofsaid trunk line andcontrolled by the change in direction of the current in one conductor thereof. 15. In a telephone system, the combination with an operators cord circuit and a trunk line terminating in an automaticconnector switch, of means for connecting said cord circuit and trunk line, a called line, means for controlling said switch over the two sides of said trunkline in parallel to connect with the called line, -a.source of current included in the controlling circuit, means controlled over the connected called line for connecting the two conductors of said trunkv line in series with said current source, a signal .1nv said cord c1rcu1t, and a relay operated over the said trunk line conductors in series to control said signal.

16. In a telephone s'ystem, the conibina- 'tion with an operators cord circuit, and a trunk line terminating in an automatic connector switch, of means for connectin said line means for controlling said switch ever-the: two sides of said trunk line in parallel 'to connect with the called line a source of current included in the controlling circuit, means controlled over'the connected called line for connecting the two conductors of said trunk line in series with said current source, a signal in said cordcireuit, and a" relay controlled by the shifting of said trunk line conductors from parallel to series con-' nection for controlling said signal.

17. In a telephone system, the combination with an operators cord circuit, and a trunk l1ne termlnatlng'in an automatlc connector switch, of means for'connecting said .cord circuit and trunk line, a called line,

means for controlling said switch over the. :two sides of said trunk line in parallel to connect with the called line, a source of current included in the, controlling circuit, means controlled over the connected called line for connecting the two conductors of said trunk line in series with said current source, a signal in said cord circuit, and a relav for controlling sald slgnal, said relay having a winding in series witheach con-.

ductor of said trunk line and controlled by the change in direction of conductor thereof. a

18. In a telephone system, a trunk line, means including a series of automatic the current inone switches for extending said trunk line to a called line, a line relay for control ling each switch, means for transmitting operati impulses over the two conductors of sai' trunk line in parallel to operate each switch,

except the last, through the medium of its line relay to extend said conductors to the line relay of the next switch, and means for disconnecting each line relay after its associated switch is operated.

' 19. In a telephone system, the combina-' rent, and aringing key in said cordcircuit tion with an automatic selector switch havidapted when said cord circuit is connected ing a double wound controlling relay, of a line whose two conductors each terminate in a winding of said relay, a battery, co'nnec tions from one pole of said battery to both windings of said relay, means for connecting both conductors of said line to theother pole of said battery, and means for intermittently interrupti g the latter connection whereby said switch may be controlled over the two line conductors in parallel, to ex- {end a connection from said first mentioned me. i

20. In combination, a line, an automatic selector switch, a double wound controlling relay 'for said switch-in bridge of saidline,

, a batteryhaving one pole connected to the junction of the windings of said relay, a

second' double wound relay in bridge of said line, means for, connecting the junction of the windings 'df said second relay. to, the

, other pole of said battery, and means for intermittently interrupting the'latter connection whereby said switch may be controlled over the two conductors of said line in parallel.

21. In a telephone system, the combination with ,.a trunk line terminating-in an automatic selector switch, of an operators cord circuit for connecting with said trunk line, a battery, a circuit for controlling said f switch, including the two conductors of said trunk line in parallel, a controlling relay in bridge thereof having its middle point connected to said battery, a second circuit including the third conductorof said cord circuit, a relay in said secondcircuit for closingsaid controlling circuit, a calling de-- vice, andmeans for including. said device in said second circuit to operate said switch,

. to extend a coimection from said men:

. tending tioned line. l I h 22. In a telephone system, a first line and a signal in bridge thereof, a second line ex-i to an automatic connector switch,

a ring ng relay in said connector switch, an

operators cord circuit, means for connecting said cord circuit with either of said lines, a ringing key adapted when the said cord circuit is connected with the manual line to project ringing current thereover to operate said signal, and means controllable by said key when the said cord circuit is connected with the second line and adapted to close a controlling circuit for said ringing relay. r

23, In a telephone system, a first line and -a signal in bridge thereof, a second line extending to an automatic connector switch, a ringing relay in said connector switch, an operators cord circuit, means for connect ing said cord circuit'with' either of said lines, sources of alternating and direct ourwith'said first line to actuate said signal through the. medium of. said alternating current source and adapted when said cord circuit -is fconnected with said second line to close a controlling circuit for said ringing relay including said direct current source. 24. In a telephone system, a connection between a calling and a called line including an operators cord circuit, a-trunk line, and an automatic connector switch, a repeating coil in said trunk line, a ringing relayin said connector switch, a grounded .source'of ringing current, a ringing key in said cord circuit adapted toco'nnect said source-of ringing current across said trunk line, a grounded battery, a second relay bridged from a conductor of said trunk line to the ungrounded pole of said battery, and

means controlledby said second relay for operating the said ringing relay;

25.- I n'a telephone system, a connection between a calling and a called line including anoperators cord circuit, a trunk line, and an automatic" connector switch, a repeating coil in said trunk'line, a ringing relay in said connector switch, a grounded source of 26, In a telephone system, a metallic cir- 'cuit talking connection between two subscr1bers"is tat1ons, a bridge across the two conductors of said circuit comprising a pair of seriallyficonnected double wound magnets,

and 'armatures for said magnets disposed at opposite ends thereof to equalize the 1mpedance of said windings. I

'27. In "a telephone system, a metallic cir- 'cuit talking connection between two subf' scribers stations, a source of current, a

bridge comprising ,a double wound relay in series with said current source for supplying talking current to one of said stations, and a double wound impedance coil included in said bridge and having its magnetic circuitarranged to balance the talking circuit. t

28. In .a telephone system, the combination'with an operatorscord circuit and a trunk line terminating in an automatic c onnector switch, of means for connecting said cord circuit and trunk line, a called line, means for controlling said switchove nthe two sides of said trunkline in parallelto connect with the called line, a source of cur rent included in the controlling circuit,

means for preventing the completion of the connection if the called line is busy and for connecting at the same time the two con.- ductors of said trunk line in series with said ,current source, a signal in the operators cord circuit, and a relay controlled, by the shifting of the conductors of said trunk linev from parallel to series connection for controlling said signal.

29. In a telephone system, the combina-- tion with an operators cord circuit and a trunk line'terminating in an automatic con-' nector switch, of means for connecting said cord circuit and trunk line, a called line, means for controlling said switch over the two sides of said trunk line in parallel to connectwith the called line, a source of current in the controlling circuit, means for preventing the completion of the connection if the called line is busy and for connecting at the same time the two conductors of said trunk line in series with said current source, means for automatically completing the connection when the called line becomes idle and for again connecting the two conductorsof said trunk line in parallel, a-signal in the said cord circuit, and a controlling-"relay for'said signal responsive to the change in direction of the current in one conductor of said trunk line. f

30. In a telephone system, an operators cord circuit, a trunk line accessible thereto and terminating in an automatic switch, a

signal, a circuit including the third conductor of said cord circuit and an impulse transmittlng relay for operating said switch, and

32. In a. telephone system, an operators' cord circuit, a. trunk line accessible thereto and terminating in an automatic switch, a circuit including the third conductor of said cord circuit, means. for interrupting said circuit, means IQSPOIISIXG to such interruptions for operating said switch, a signal in said cord circuit, and a circuit for controlling said signal including the third conductor of said cord circuit.-. Y

33. In a telephone system, an operators cord circuit, a trunk line accessible thereto and terminatingin an automatic switch, a I

signal, a circuit including the third conductor of said cord'circuit and an impulse transmitting relay for controlling said switch, I

said relay having'a low and high resistance winding in series, a second relay in said circuit for controlling said signal, means for normally short-circuiting said high resist- 'ance winding to render said second relay operatlve and means for removing said short circuit to denergize the same.

34. In a telephone system, an operators cord circuit, a trunk line accessible thereto and terminating 1n an automatic switch, a

circuit including the third conductor of said cord circuit and having a normally connected branch and a normally disconnected branch, means for substituting the latter branch in said circuit, means for then sendl'llg current impulses over sald circult, means.

responsive to said impulses'for controlling said, switch, a signal, and means'for controlling said signal over said circuit after said branches are restored to normal 'con dition.

35. In a telephone system,ian operators cord circuit, a trunkline accessible thereto and terminating in an automatic switch, av

circuit including the third conductor'of said cord circuit and having a normally connected branch and a normally disconnected. branch, means for substituting the latter branch in said circuit, .means for then sendmg current impulses over sald circuit, means responsive to said impulses for controlling said switch, a signal, a relay in said normally connected branch for controllin said signal, and means operable after said ranches'are restored to normal condition for controlling said relay over said circuit.

36. In a telephone system, a calling line and a trunk line, said trunk line terminating in an automatic switch, a called line ac-' cessible to said switch, means lncludmg an operators cord circuit for connecting the calling line with s aid trunk line, a signal in said cord circuit, a controlling circuit including the third conductorof said cord circuit and provided with two branches, means I responsive to interruptions of one of said branches for operating said switch to connect with the called line, and means actuated upon the response of the called subscriber.

for altering the electrical conditionof said controllin circuit to control said signal throu h the medium of the other branch.

37. n a telephone system, means includ-' ing an operators cord circuit and a seriesof automatic switches for connecting acalling and called line, a signal at the cord circuit, a.

circuit including the third conductor of said cord circuit, and means for operating-said switches and for controlling said signal over said circuit.

38. In a telephone system, means includ- "ing an operators cord circuit, a trunk line, and an automatlc swltchfor connectmg acalling and called line, a signal'at the cord circuit, a circuit includin the two sides of said trunk line in para el for operating said switch, and a metallic circuit including the two sides of said trunk line in series for controlling said signal, said last mentioned circuit energized when the called subscriber closes a talking circuit over his line. 10

Signed 'by' me at Chica 0, Cook county, State of Illinois, this first ay'of June, 1916.

' BERNARD ID. wI'LLis. 

